Metal gauze



Dec. 28, 1937. w. H. HERAEUS METAL GAUZE Filed Aug. 3, 1935 Patented Dec. 28, 1937 UNITEDSTATESV ME'TAL GAUZE Wilhelin Heinrich Heraeus,'Hanau, Germany, as-

signertome firm W. CpHeraeus, G. m.

Hanan, Germany 7 Application August s, 1935, Serial No. 34,551

In Germany March23, 1935 1 Claim. (01. 23-234) My invention relates to metal gauze. 7 It is an object of my invention to provide metal gauze which possesses the highest mechanical strength obtainable. v t f j To this end, I make the warp wires of the gauze of harder, and the weft wires of softer -metal. r a

Metal gauzeas'ma'de heretofore has the drawback that the mechanical strength is not distributed evenly. over the gauze, and this is due to-'the weaving of the gauze; The weft wires remain substantially straight in the weavingof the gauze, while the warp wires are threaded about the weft wires at comparatively sharp curvatures. In a gauze embodying my invention, the warp wiresare used as drawn,'i. e., in their normal hard condition, but, as'they are curved, they can yield'to a certain extent. On the other hand, the weft wires which are substantially straight, are made more yielding by softening them. In a gauze as described, whosewarp wires are harder, and whose weft wires are softer, the mechanical strength is distributed more evenly, and so the overall strength of the gauze becomes a maxia mum.

. oxidizing ammonia, but it 'is understood that I am not limited to a gauze for this purpose but that my novel gauze may be used wherever high mechanical strength is required.

Catalyst gauze is usually'made of platinum,

why the weft wires are the first to fail when the gauze. is bulged.

By making the weft wires of softer metal, according to my invention, this drawback is eliminated and the life of the catalyst gauze is much prolonged.v

j In the accompanying drawing, I have illustrated by way of example a catalyst gauze, drawn to a magnified scale.

In the drawing Fig. l is a plan view of the gauze,

Fig. 2 is a section on the line II--II in Fig. 1,

Fig. 3 is a section on the line III-III in Fig. 1, and

Fig. 41s a perspective illustration of a modified gauze.

If the wires of the gauze are of pure platinum,

its warp wires a are woven-into the gauze as drawn, i; e., withthe hardness partedto them by fine drawing, while" the weft'wires; hare softened by annealing and, upon being'woven into the gauze, are not pulled ta'ut as sharply-as ifthey'were as hard as the warp-wires, but hug the warp wires onaccouiit of their softness'fso that the warp and the" weft threads ar evenly interwoven in the finished gauze. v

Fig. 2 shows the gauze withstraight warpwires 'a, and curved weft 'wires b, Fig. 3 shows straight weft Wires b and curved warp wires 01., and Fig.. 4 shows both wires curved.

It has beenfound that catalyst gauze made of platinum-rhodium alloy is superior in some respects to gauze of pure platinum wires as a catalyst for the burning of ammonia, its superiority residing principally in the higher conversions of ammonia which increase with the percentage of rhodium in the alloy.

However, the percentage of rhodium in the alloy is not unlimited. The yield of nitrogen with a' 10% rhodium alloy is appreciably higher than with a 5% alloy, but wires of the 10% alloy tend to become brittle in the operation of the catalyst, which makes the gauze less durable. Gauzes with wires of 5% alloy are more durable but the yield is also less. Notwithstanding this,

* the nitrogen industry prefers low-alloy gauze on account of its reliability.

.Wires of alloy containing more than 10% rho-' dium are not used in practice because the manufacture of such wires, and the weaving thereof into gauze, present certain difficulties while, on the'other hand, the increase of conversions which can be obtained with the higher rhodium percentages, is not very considerable.

As mentioned, the weft wires are principallyv responsible for theshort life of gauze as made heretofore. Thehigh-rhodium wires are harder than the low-rhodium wires, and therefore, in a gauze embodying my invention, the high-rhodium wires make up the warp, and the softer lowrhodium wires make. up the weft. It is also possialloy, and to anneal them.

By these means, the weft wires are softer than the warp wires, and the soft weft threads are more expansible, so that they engage the warp threads in a sinus curve, and the difference in the deflection of the warp and weft threads, and in the stress to which the wires are subjected, is eliminated.

In a gauze of the kind described, the mechanical weakness of gauzes consisting of high-rhodium wires, such as wires with 10% of rhodium, is absent, while at the same time the conversions are higher than with gauze consisting of lowrhodium wires, say, 5% of rhodium. For instance, a gauze having 5% weft wires, and 10% warp wires, the weft wires being softer than the warp wires on account of their lower percentage of rhodium, will produce the same conversions as a gauze whose warp and weft wires are of 7.5% rhodium alloy, but is better than the 7.5% gauze as to its mechanical properties. It is also possible to make gauze of, say, weft wires with a 5%, and warp wires with a 15% rhodium alloy, and to obtain the same conversions as with a gauze of 10% rhodium wires, but the gauze of low and highrhodium wires has the better mechanical properties. Lastly, the warp and the weft wires may be made of the same high-rhodium alloy, Say, 7.5%, or even 10%, of rhodium, after the wires have been softened by annealing.

It follows that with a gauze according to my invention, one may select the. conversions to be obtained near the upper limit of those obtained heretofore, and, at the same time, one may improve very much the mechanical properties of the gauze, or, if one is satisfied with the same durability as that of the gauze as made heretofore, still higher conversions will be obtained.

With respect to weaving, my novel gauze weaves more uniformly than a gauze whose wires are of equal hardness, because the softer wires make up the weft, and the harder wires make up the warp, as described.

It is understood that I am not limited to the use of wires of pure metal, nor of alloy, nor to the combination of pure wires and alloy wires. Nor am I limited to any definite metal, alloy, or percentage of constituents in an alloy, but my invention includes all kinds of metal gauze whose wires have distinct mechanical properties and are so arranged in the gauze with consideration of their mechanical properties, that the stress is distributed evenly, or substantially so, all over the gauze. Nor am I limited to gauze which is to be used as a catalyst, this being merely described and shown by way of example.

I claim:

A catalyst of metal gauze consisting of wires of platinum rhodium alloy in which the weft wires are of lower rhodium content and the Warp wires are of higherrhodium content for the purpose of making the weft wires softer to conform to the positions of the Warp wires and distribute stress evenly throughout the gauze, both of said wires being substantially circular in cross section throughout their length.

WILHELM HEINRICH HERAEUS. 

